Wireless power transfer to devices (including wireless charging) such as smart phones, tablets, personal digital assistants and other mobile platforms, is becoming increasingly common. Typically, the devices receiving the wireless power (or the device to be charged) are placed on a power transmitting platform (like a charging pad) that includes a Power Transmitting Unit (PTU). The PTU provides power to the devices, wirelessly, through inductive coupling (including magnetic resonance, as is used, for example, in the Rezence® wireless power transfer technology) of an electromagnetic field between the devices. A Power Receiving Unit (PRU) in the device is configured to receive this inductive power and use it to charge the device. An initial communication may be established between the PTU and the PRU through modulation of the inductive electromagnetic field. Generally, after the initial communication is established, a secondary communication mechanism, which may be more efficient, is employed to exchange further information and negotiate power transfer parameters, etc. The secondary communication may be through a wireless connection such as, for example Bluetooth®.
A PTU may be configured to support simultaneous power transfer to (and communication with) multiple PRUs. Additionally, in some environments, there may be multiple PTUs in operation. PRUs are typically identified to the PTU through a PRU identification number that may be transmitted, for example, over the wireless connection. It is possible, therefore, that a PRU may present a fraudulent identification to the PTU or that a PTU may inadvertently detect a PRU that is being charged by another PTU. There is generally no reliable method for a PTU to verify that it is communicating with a PRU that is located on top of it or otherwise within range of the inductive coupling. Additionally, the wireless connection is not encrypted and may therefore be snooped by other devices, thus preventing the transmission of confidential or sensitive information between the PTU and the PRU.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art.